Replacing a built-in method of a module object instance

[David Hirschfield]

I have a need to replace one of the built-in methods of an arbitrary
instance of a module in some python code I'm writing.

Specifically, I want to replace the __getattribute__() method of the
module I'm handed with my own __getattribute__() method which will do
some special work on the attribute before letting the normal attribute
lookup continue.

I'm not sure how this would be done. I've looked at all the
documentation on customizing classes and creating instance methods...but
I think I'm missing something about how built-in methods are defined for
built-in types, and where I'd have to replace it. I tried this naive
approach, which doesn't work:

m = <module instance>

def __getattribute__(self, attr):
print "modified getattribute:",attr
return object.__getattribute__(self, attr)

import types
m.__getattribute__ = types.MethodType(__getattribute__,m)

It seems to create an appropriately named method on the module instance,
but that method isn't called when doing any attribute lookups, so
something's not right.
Any ideas? Is this even possible?
Thanks in advance!
-David

 

[Peter Otten]

I have a need to replace one of the built-in methods of an arbitrary
instance of a module in some python code I'm writing.

Specifically, I want to replace the __getattribute__() method of the
module I'm handed with my own __getattribute__() method which will do
some special work on the attribute before letting the normal attribute
lookup continue.

I'm not sure how this would be done. I've looked at all the
documentation on customizing classes and creating instance methods...but
I think I'm missing something about how built-in methods are defined for
built-in types, and where I'd have to replace it. I tried this naive
approach, which doesn't work:

m = <module instance>

def __getattribute__(self, attr):
print "modified getattribute:",attr
return object.__getattribute__(self, attr)

import types
m.__getattribute__ = types.MethodType(__getattribute__,m)

It seems to create an appropriately named method on the module instance,
but that method isn't called when doing any attribute lookups, so
something's not right.
Any ideas? Is this even possible?

Special methods are looked up in the type, not the instance, and you cannot
set attributes of the module type.

As a workaround you can write a wrapper class and put that into the
sys.modules module cache:
.... def __init__(self, module):
.... self.__module = module
.... def __getattr__(self, name):
.... try:
.... return getattr(self.__module, name.lower())
.... except AttributeError:
.... def dummy(*args): pass
.... return dummy
....

import shutil
import sys
sys.modules["shutil"] = Module(shutil)
import shutil
shutil.MOVE

shutil.yadda

<function dummy at 0x7f20f9b7d6e0>

Peter